The apartment I was staying in was the same layout as the one which Maddie was taken from, I was able to recreate the vacuum spoken about in Kate McCanns account involving the children's bedroom door slamming, and the curtains flailing at the open window / shutter repeatedly without deviation providing the bedroom window and shutter was open and raised, the bedroom door slightly ajar, and both the patio door, and the front door were both open all at one and the same time! What this alerted me to at the time of these experiments was the very strong possibility that someone was already inside the apartment waiting for Kate to come, or that the person concerned re-entered the apartment just after Kate arrived there! The key feature being that someone opened the front door on the roadside of the apartment which caused the bedroom door to slam shut! The front door must have remained open long enough for Kate to push the door back open and for her to go to the bedroom window where the curtains were flailing to notice that the window was open and the steel shutter raised!
Kate does not state how long this phenomena lasted for?